JP5361800B2 - Optical waveguide type Q switch element and Q switch laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical waveguide type q-switching element and a q-switching laser device that realize high extinction ratio, a super compact size, and low driving voltage. <P>SOLUTION: An optical waveguide type q-switching element is provided with an optical waveguide 3 comprised of a core 5 and clads 4a, 4b, and has a plane waveguide structure; light loss means 7a, 7b and electrodes 2a, 2b; and a q-switching driving device 6 that applies voltage to the electrodes 2a, 2b. The clads 4a, 4b are provided on the upper and lower sides of the core 5; the light loss means 7a, 7b are provided on the upper side of the clad 4a and the lower side of the clad 4b, respectively; and the electrodes 2a, 2b are provided on the upper side of the light loss means 7a and the lower side of the light loss means 7b, respectively. The refractive index of the core 5 changes when an electric field is applied owing to the electro-optical effect: the refractive index of the core 5 becomes higher than the refractive index of the clad when the electric field is not applied; while the high potential side of the refractive index of the core 5 becomes lower than the refractive index of the clad when the electric field is applied. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention provides an optical waveguide type Q switch element (for example, a planar waveguide type Q switch element) using an electro-optic effect, and a giant pulse is obtained by changing the Q value in the resonator using the Q switch element. Q-switched laser device for the same.

Conventionally, as an example of a Q switch element, a Q switch element using an electro-optic crystal having a Pockels cell effect has been proposed (see, for example, Patent Document 1).
This type of Q-switch element is configured in a resonator by combining a polarization separation splitter and a polarizer such as a thin film polarizer, and electrically transmits the polarization direction of the Pockels cell to transmit the polarizer. The Q switch pulse is obtained by changing the ratio of the component and the reflection component and changing the Q value in the resonator.

Conventionally, as an example of an optical waveguide type Q switch element, a Q switch element using a saturable absorber as an optical waveguide material has also been proposed (for example, see Non-Patent Document 1).
In this type of optical waveguide type Q switch element, the saturable absorber is a substance that becomes gradually transparent when absorbing light, and when inserted into the resonator, it becomes a loss at the start of excitation and gradually suppresses laser oscillation. When it becomes transparent and the gain becomes larger than the loss, the laser oscillation is rapidly started to obtain the Q switch pulse.

  Furthermore, conventionally, a resonator comprising an output mirror and a total reflection mirror, a laser light source (laser rod, polarizer and Pockels cell) disposed in the resonator, and a flash lamp for exciting the laser rod, There has been proposed a Q-switched laser device composed of a Pockels cell driving circuit that changes the voltage applied to the Pockels cell (see, for example, Patent Document 2).

  In this type of Q-switched laser device, the polarization direction in the resonator is controlled by the voltage applied to the Pockels cell, and the Q value in the resonator is changed by the combination with the polarizer so as to obtain a giant pulse. It has become.

JP-A-9-64448 (page 7, FIG. 1) Japanese Patent Laid-Open No. 61-168979 (page 5, FIG. 1)

J. et al. I. Mackenzie, “End-pumped, passive Q-Switched Yb: YAG double-clad waveguide laser”, OPTICS LETTERS / Vol. 27, NO. 24 / December 15, 2002

In the case of the conventional Q switch element and the Q switch laser apparatus described in Patent Document 1 and the Q switch laser described in Patent Document 2, a high voltage (several hundreds of times) is used to rotate the polarization by 90 °. Several kV) and a switching circuit that can drive a switching voltage with a fast fall time or rise time (about 10 ns) is required, and a polarization control element such as a polarizer must be inserted in the resonator. Therefore, there is a problem that the number of parts increases.
Further, when a material such as Nd: YAG is used for the laser medium, there is a problem that a depolarization loss (depolarization loss) due to thermal birefringence occurs and efficiency is lowered.

Further, the optical waveguide type Q switch element described in Non-Patent Document 1 has a problem that the efficiency is lowered due to the residual loss of the saturable absorber.
Further, in order to increase the peak power, it is necessary to increase the optical density of the saturable absorber, and the residual loss at this time increases in proportion to the optical density, so the efficiency reduction is large. There was a problem of becoming.
Furthermore, saturable absorbers have a problem in that it is difficult to accurately control the oscillation timing of pulses, and the oscillation timing varies greatly due to variations in the intensity of excitation light.

The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an optical waveguide Q-switch element that realizes a high extinction ratio, ultra-small size, and low driving voltage.
Another object of the Q-switch laser apparatus using an optical waveguide Q-switch element is to realize a precise timing control with a small number of parts, a small size and high efficiency.

  The optical waveguide type Q switching element according to the present invention is an optical waveguide having a planar waveguide structure composed of a core and a clad, optical loss means and electrodes provided on the upper and lower surfaces of the optical waveguide, and a voltage applied to the electrodes in an on / off manner. An optical waveguide type Q switch element comprising: a clad provided on the upper and lower surfaces of the core to confine light in the core; The electrode is made of a material having high electrical conductivity, parallel to the plane of the optical loss means, and is provided on both end faces opposite to the core. And provided on both end faces facing the clad and electrically connected to the Q switch driving device, the core has an electro-optic crystal, and an electric field is applied between the electrodes on both end faces. It is made of a material whose refractive index changes due to the gas-optic effect, and the refractive index in the core is higher than the refractive index of the upper and lower clads when no electric field is applied, and is positive between the electrodes on both ends. When the electric field is applied and the upper electrode becomes high potential and the lower electrode becomes low potential, the refractive index of the upper cladding is lower than that of the upper cladding and higher than that of the lower cladding, When a negative electric field is applied between the electrodes on both end faces, the upper electrode becomes a low potential and the lower electrode becomes a high potential, the refractive index of the lower clad is lower than that of the lower clad. It is set to be higher than the refractive index of the cladding.

  According to the present invention, the optical confinement function of the clad film is removed by reversing the refractive index difference between the optical waveguide and the clad by the optical deflection due to the electro-optic effect or the refractive index change in the optical waveguide. In addition, an optical waveguide type Q switch element realizing a high extinction ratio and miniaturization can be obtained without using a Pockels cell or a saturable absorber using polarized light.

It is a perspective view which shows the optical waveguide type Q switch element concerning Embodiment 1 of this invention. It is sectional drawing by the A-A 'line in FIG. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 1 when an electric field is not applied with sectional drawing. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 1 at the time of an electric field application with sectional drawing. It is a characteristic view which shows the calculation result of the relationship between the refractive index change in an optical waveguide, and an electric field. It is a characteristic diagram showing the calculation results of the relationship between KTN and refractive index and the applied voltage of _Ta 2 _{O 5 which has} a thickness of 40μm on the core 5. It is a characteristic view which shows the calculation result of the incident angle dependence of various metal materials. It is a characteristic view which shows the calculation result of the incident angle dependence of various metal materials. It is a perspective view which shows the other structural example of Embodiment 1 of this invention. It is explanatory drawing which shows the operation | movement of FIG. 9 when an electric field is not applied with sectional drawing by a B-B 'line | wire. It is explanatory drawing which shows operation | movement of FIG. 9 at the time of an electric field application with sectional drawing by a B-B 'line. It is a perspective view which shows the optical waveguide type Q switch element concerning Embodiment 2 of this invention. It is sectional drawing by the C-C 'line in FIG. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 12 when an electric field is not applied with sectional drawing. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 12 at the time of an electric field application with sectional drawing. It is a perspective view which shows the optical waveguide type Q switch element concerning Embodiment 3 of this invention. It is sectional drawing by the D-D 'line in FIG. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 16 when an electric field is not applied with sectional drawing. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 16 at the time of an electric field application with sectional drawing. It is a perspective view which shows the optical waveguide type Q switch element concerning Embodiment 4 of this invention. It is sectional drawing by the E-E 'line | wire in FIG. FIG. 21 is an explanatory view showing the operation of the optical waveguide type Q switch element of FIG. 20 in a cross-sectional view when no electric field is applied. It is explanatory drawing which shows operation | movement of the optical waveguide type Q switch element of FIG. 20 at the time of an electric field application with sectional drawing. It is a perspective view which shows the Q switch laser based on Embodiment 5 of this invention. It is a perspective view which shows the other structural example of the Q switch laser based on Embodiment 5 of this invention.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing an optical waveguide Q-switch element 1 according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA ′ in FIG.
1 and 2, an optical waveguide type Q switch element 1 has a planar waveguide structure (planar waveguide type Q switch element), and includes upper and lower electrodes 2a and 2b, upper and lower clads 4a and 4b, and a core. 5, a Q switch driving device 6, and light loss means 7 a and 7 b on the upper and lower surfaces.

Clads 4a and 4b are provided on both end faces of the core 5 parallel to the xz plane.
Optical loss means 7 a and 7 b are provided on both end faces of the clads 4 a and 4 b that are parallel to the xz plane and that face the core 5.
Furthermore, electrodes 2a and 2b are provided on both end faces parallel to the xz plane of the light loss means 7a and 7b and facing the clads 4a and 4b, and the electrodes 2a on both end faces (upper and lower faces), The output terminal of the Q switch driving device 6 is electrically connected to each of 2b.

Incident light L1 incident on the optical waveguide 3 propagates in the core 5 in the z-axis direction and is emitted as outgoing light L2. That is, the z axis is parallel to the optical axis with respect to the optical waveguide 3.
An x axis parallel to the xz plane direction of the optical waveguide 3 and perpendicular to the light propagation direction (z axis) is a slow axis with respect to the optical waveguide 3. The y axis perpendicular to the xz plane direction of the optical waveguide 3 is the fast axis with respect to the optical waveguide 3.
The planar waveguide structure refers to the optical waveguide 3 that confines the incident light L1 by the layered structure and propagates the light wave only in the direction along the xz plane.

Next, the light propagation operation according to the first embodiment of the present invention shown in FIGS. 1 and 2 will be described with reference to FIGS.
3 and 4 are explanatory diagrams showing the propagation operation of the incident light L1, FIG. 3 shows the operation when no electric field is applied between the electrode 2a and the electrode 2b, and FIG. 4 shows the electrode 2a and the electrode. The operation when an electric field is applied between 2b is shown.

  FIG. 5 is an explanatory diagram showing a distribution state of the refractive index n in the optical waveguide 3, and FIG. 5 (a) shows a case where an electric field is not applied between the electrode 2a and the electrode 2b. (B) has shown the case where an electric field is applied between the electrode 2a and the electrode 2b.

  First, as shown in FIG. 3, when no electric field is applied between the electrode 2a and the electrode 2b, when the light L1 is incident from the incident surface 5a of the core 5 and propagates through the optical waveguide 3, the y-axis direction As for optical waveguide mode light having a propagation angle lower than the critical angle θc at the interface between the core 5 and the upper cladding 4a and the interface between the core 5 and the lower cladding 4b.

Therefore, when no electric field is applied (FIG. 3), the optical waveguide mode light having a propagation angle lower than the critical angle θc among the incident light L1 in the y-axis direction propagates through the optical waveguide 3 with almost no loss. Then, it is emitted from the exit surface 5b of the core 5 as the emitted light L2.
Further, with respect to the x-axis direction, the light L1 propagates in parallel with the z-axis direction (optical path direction) and is emitted from the emission surface 5b of the core 5 as emitted light L2.

  On the other hand, when an electric field is applied between the electrode 2a and the electrode 2b as shown in FIG. 4, when the light L1 enters from the incident surface 5a of the core 5 and propagates through the optical waveguide 3, the y-axis direction As for the optical waveguide mode light having a propagation angle lower than the critical angle θc, it is totally reflected at the interface between the core 5 and the lower clad 4b.

However, since the refractive index of the core 5 (to be described later with reference to FIG. 5) is changed by applying an electric field, the incident light L1 leaks through the cladding 4a to the optical loss means 7a at the interface between the core 5 and the upper cladding 4a. However, a part of the light L1 is emitted from the emission surface 5b of the core 5 in a state attenuated by the light loss means 7a.
Further, with respect to the x-axis direction, the light L1 propagates in parallel with the z-axis direction and is emitted from the emission surface 5b of the core 5 as emitted light L2.

Next, a change in the refractive index n when a voltage is applied to the core 5 will be described with reference to FIG.
FIG. 5 is an explanatory diagram showing the refractive index n in the optical waveguide 3 of the optical waveguide type Q switch element 1, and the refractive index states corresponding to the respective positions (y-axis direction) of the core 5 and the clads 4a and 4b are as follows. It is shown in relation to the presence or absence of an electric field.

  FIG. 5A shows a distribution state of the refractive index n in the optical waveguide 3 when no electric field is applied between the electrode 2a and the electrode 2b, and FIG. 5B shows the relationship between the electrode 2a and the electrode 2b. The distribution state of the refractive index n in the optical waveguide 3 when a positive electric field is applied therebetween is shown.

First, a change in the refractive index n in the optical waveguide 3 when a positive electric field is applied between the electrode 2a and the electrode 2b will be described.
As in FIG. 5 (a), when an electric field is not applied between the electrodes 2a and 2b, the refractive index n ₁ of the core 5, the cladding 4a, higher than the refractive index n ₂ of 4b It is in.
On the other hand, as shown in FIG. 5B, when a positive electric field is applied between the electrode 2a and the electrode 2b, the electrode 2a becomes a high potential and the electrode 2b becomes a low potential, the refractive index in the core 5 is increased. n ₁ changes due to the electro-optic effect of the core 5 and is lower than the refractive index n ₂ of the cladding 4 b on the upper electrode 2 a side and higher than the refractive index n ₂ of the cladding 4 a on the lower electrode 2 b side. Become.

  Although not shown, when a negative electric field is applied between the electrode 2a and the electrode 2b, the electrode 2a has a low potential, and the electrode 2b has a high potential, the refractive index in the core 5 is 5B, the refractive index is lower than the refractive index of the cladding 4b on the lower electrode 2b side and higher than the refractive index of the cladding 4a on the upper electrode 2a side.

  In the optical waveguide type Q switching element 1 of FIGS. 1 to 4, the clad 4a, 4b is made of a material whose refractive index is lower than the refractive index of the core 5 when no electric field is applied (FIG. 5 (a)). When a positive electric field is applied (FIG. 5B), the refractive index is higher than the refractive index of the core 5 on the high potential (upper surface electrode 2a) side, and the lower potential (lower surface A material that is lower than the refractive index of the core 5 on the electrode 2b) side is used.

Further, as the material of the core 5, a material having a high electro-optic constant is used, and the Pockels cell effect showing the first-order electro-optic effect (the refractive index change Δn is proportional to the applied electric field E) or the second-order electricity. Those having a Kerr effect showing an optical effect (refractive index change Δn is proportional to the square of the applied electric field E) are selected. Specifically, lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), SrBaNb ₂ O ₆ (SBN), KTaNbO ₃ (KTN), or the like is desirable.

Relationship between the Pockels refractive index change due to the cell effect Δn and the applied electric field E [V / m] is the refractive index _{n o,} the electro-optic coefficient _r eff [m / V], and the applied voltage V [V], the optical waveguide Using the thickness d [m], the following equation (1) is obtained.

Δn = (n _o ) ³ r _eff E
= (N _o ) ³ r _eff (V / d) (1)

The relationship between the applied and the refractive index change due to the Kerr effect Δn field E [V / m] is the refractive index _{n o,} by using the kerr constant ^{_{S eff [m 2 / V 2}} ], the following equation (2 ).

^{_{Δn = 0.5 (n o) 3}} S eff E 2 ··· (2)

FIG. 6 is an explanatory diagram showing the relationship between the refractive indexes n ₁ and n ₂ of the core 5 and the clads 4a and 4b and the applied voltage. For example, the refractive index n ₁ = 2.18 of the core 5 (applied voltage = 0). , Kerr coefficient S _eff = −4.8 × 10 ⁻¹⁵ [m ² / V ² ] (equivalent to KTN), refractive index n _{2 of the} clads 4a and 4b = 2.08 (equivalent to Ta ₂ O ₅ ), optical waveguide thickness The characteristic with respect to the applied voltage when d = 40 μm is shown.

As is apparent from FIG. 6, when a voltage of about 81 [V] is applied from the voltage = 0 state, the refractive index n ₁ of the core 5 becomes smaller than the refractive index n _{2 of the} cladding 4a, relationship of the refractive index between the core 5 and the cladding 4a is reversed from _"n 1> _{n 2"} to _"n 1 _{<n 2."}

  When an electric field is applied between the electrode 2a and the electrode 2b, the light L1 in the core 5 is deflected. Therefore, a light loss means (light absorption means) 7b is provided between the electrode 2b on the lower surface and the clad 4b. The deflection angle θd of the propagation mode in the optical waveguide 3 is set larger than the critical angle θc at the interface between the core 5 and the clad 4b so that a part of the light L1 is refracted into the clad 4b. It is possible to increase the loss effect when an electric field is applied.

The relationship between the critical angle θc and the refractive indexes n ₁ and n ₂ of the core 5 and the clads 4a and 4b is expressed by the following equation (3).

θc = sin ⁻¹ {√ (n ₁ ² −n ₂ ² ) / n ₁ } (3)

In addition, when an electric field is applied between the electrode 2a and the electrode 2b, the light deflection angle θd is the refractive index n ₁ of the core 5, the kerr constant S _eff , the interaction length h of the crystal, the optical waveguide Using the thickness d and the electric field E, the following equation (4) is obtained.

θd = −9 / 8 (n ₁ ² ) S _eff (h / d) E ² (4)

For example, the refractive index n ₁ = 2.18 of the core 5, the kerr coefficient S _eff = −4.8 × 10 ⁻¹⁵ [m ² / V ² ] (equivalent to KTN), and the refractive index n ₂ = 2 of the clads 4a and 4b .08 (corresponding to Ta ₂ O ₅ ), the critical angle θc = 17.4 [°] is obtained from the equation (3).
Here, when the optical waveguide thickness (core thickness) d = 40 μm and the voltage 81 [V] is applied, the deflection angle θd at the interaction length h = 60 μm is larger than the critical angle θc from FIG. Become.

In the optical waveguide type Q switch element 1, it is desirable to form the light loss means 7a and 7b with a material having a low reflectance in order to increase the attenuation rate of the propagation light.
Since the light L1 propagating through the optical waveguide 3 is reflected many times by the optical loss means 7a and 7b as shown in FIGS. 3 and 4, the incident angle to the optical loss means 7a and 7b is wide.

7 and 8 are characteristic diagrams showing calculation results of the dependence of the reflectance on the incident angle [°] to various metal materials.
7 and 8, FIG. 7A is a characteristic diagram of silver, FIG. 7B is a characteristic diagram of copper, FIG. 7C is a characteristic diagram of nickel, and FIG. 7D is a characteristic diagram of gold. ) Shows the characteristic of lead, FIG. 8B shows the characteristic of aluminum, FIG. 8C shows the characteristic of chromium, and FIG. 8D shows the characteristic of titanium.

Here, characteristics of light having a wavelength of 1064 nm that are generally used as laser oscillation light are shown.
In FIGS. 7 and 8, the characteristic for S-polarized light (polarization direction perpendicular to the incident plane) is shown by a curve a, and the characteristic for P-polarized light (polarization direction horizontal to the incident plane) is shown by a curve b. Is shown.

  7 and 8, when the optical loss means 7a and 7b are provided on the upper and lower surfaces of the clads 4a and 4b, the TM (Transverse Magnetic) polarization mode is incident on the P-polarized light. The nickel of FIG. 8, lead of FIG. 8 (a), chromium of FIG. 8 (c) and FIG. 8 (d) have a reflectance of 0.15 to 0.7 at an incident angle of 80 [°] or less.

  Therefore, since nickel, lead, chromium and titanium give a large loss to the light leaked to the outside of the clads 4a and 4b, any one of nickel, lead, chromium and titanium can be used as the light loss means 7a and 7b. It is desirable to use

  Further, in the optical waveguide type Q switch element 1, a condition required as a material of the electrodes 2a and 2b is high electrical conductivity. For example, a metal film such as gold, silver, copper, aluminum, or chromium is used as the electrode. It is desirable to use as 2a and 2b. The electrodes 2a and 2b can be used in common as the light loss means 7a and 7b.

In order to increase the attenuation of propagating light, it is also effective to increase the loss effect by scattering light by roughening the interfaces of the clads 4a and 4b in contact with the optical loss means 7a and 7b.
In this case, for example, it is effective to roughen the interfaces of the clads 4a and 4b in contact with the light loss means 7a and 7b by performing reactive ion etching or back sputtering.

Further, although not mentioned in FIGS. 1 to 4, it is also effective to provide a transparent block 8 having a tapered shape in place of the light loss means 7a on the upper surface as shown in FIG.
FIG. 9 is a perspective view showing another configuration example of the first embodiment of the present invention. The same components as those described above (see FIG. 1) are denoted by the same reference numerals, and detailed description thereof is omitted.

  9 to 11, the transparent block 8 has a dimension (thickness) in the y-axis direction that gradually increases from the incident surface 5a of the core 5 constituting the optical waveguide 3 toward the output surface 5b. Has a tapered shape.

10 and 11 are explanatory views showing the light propagation operation by the configuration of FIG. 9 in a cross-sectional view along the line BB ′.
FIG. 10 shows an operation when no electric field is applied between the electrode 2a and the electrode 2b, and FIG. 11 shows an operation when an electric field is applied between the electrode 2a and the electrode 2b. ing.

The operation according to another configuration example of the first embodiment of the present invention shown in FIGS. 9 to 11 will be described below.
As shown in FIG. 10, when no electric field is applied between the electrode 2a and the electrode 2b, when the light L1 is incident from the incident surface 5a of the core 5 and propagates through the optical waveguide 3, the y-axis direction is as follows. The optical waveguide mode light having a propagation angle lower than the critical angle is totally reflected at the interface between the core 5 and the upper cladding 4a and at the interface between the core 5 and the lower cladding 4b.

Therefore, when an electric field is not applied (FIG. 10), the optical waveguide mode light having a propagation angle lower than the critical angle θc among the incident light L1 in the y-axis direction propagates through the optical waveguide 3 with almost no loss. Then, it is emitted from the exit surface 5b of the core 5 as the emitted light L2.
Further, with respect to the x-axis direction, the light L1 propagates in parallel with the z-axis direction and is emitted from the emission surface 5b of the core 5 as emitted light L2.

  On the other hand, when an electric field is applied between the electrode 2a and the electrode 2b as shown in FIG. 11, when the light L1 enters from the incident surface 5a of the core 5 and propagates through the optical waveguide 3, the y-axis direction With respect to the optical waveguide mode light having a propagation angle lower than the critical angle, it is totally reflected at the interface between the core 5 and the lower clad 4b.

  However, at the interface between the core 5 and the upper clad 4a, due to a change in the refractive index of the core 5, it passes through the clad 4a and leaks to the transparent block 8, and is reflected at the interface between the transparent block 8 and the electrode 2a. As shown, the light is emitted from the end face 8 b of the transparent block 8 without entering the core 5.

  As described above, the optical waveguide type Q switching element 1 according to the first embodiment (FIGS. 1 to 11) of the present invention includes the optical waveguide 3 having the planar waveguide structure including the core 5 and the clads 4a and 4b, the optical waveguide Optical loss means 7a, 7b (transparent blocks 8, 7b) and electrodes 2a, 2b provided on the upper and lower surfaces of the waveguide 3 and a Q switch driving device 6 for applying a voltage to the electrodes 2a, 2b in an on / off manner are provided. ing.

The clads 4 a and 4 b are provided on the upper and lower surfaces of the core 5 in order to confine light in the core 5.
The light loss means 7 a and 7 b are made of a material or structure that attenuates light when contacted, and are provided on both end faces that are parallel to the plane of the clads 4 a and 4 b and that face the core 5.

  The electrodes 2a and 2b are made of a material having high electrical conductivity, and are provided on both end faces parallel to the plane of the optical loss means 7a and 7b and facing the clads 4a and 4b. Connected.

That is, _clads 4a and 4b are provided on the upper and lower surfaces of an optical waveguide (planar waveguide) 3 made of a crystal having a high electro-optic constant r _eff , and optical loss means 7a and 7b are provided on the upper and lower surfaces of the clads 4a and 4b. Electrodes 2a and 2b are provided on the outer upper and lower surfaces of the light loss means 7a and 7b, and a Q switch driving device 6 electrically connected between the electrodes 2a and 2b is provided.

The core 5 includes an electro-optic crystal, and is made of a material whose refractive index changes due to an electro-optic effect when an electric field is applied between the electrodes 2a and 2b on both end faces.
The refractive index n ₁ in the core 5 (FIG. 5A) is set to be higher than the refractive index n ₂ of the upper and lower claddings 4a and 4b when no electric field is applied.

The refractive index n ₁ in the core 5 (FIG. 5 (b)) is such that a positive electric field is applied between the electrodes 2a and 2b on both end faces, the upper electrode 2a becomes high potential, If the electrode 2b becomes low potential, and is set to be higher than the refractive index n ₂ of lower than the refractive index n ₂ of the top surface of the clad 4a, and the lower surface of the clad 4b.

The refractive index n ₁ in the core 5 is such that a negative electric field is applied between the electrodes 2a and 2b on both end surfaces, the upper electrode 2a has a low potential, and the lower electrode 2b has a high potential. In this case, the refractive index n ₂ is set lower than the refractive index n ₂ of the lower cladding 4 b and higher than the refractive index n ₂ of the upper cladding.

The optical waveguide 3 is made of KTN, the clads 4a and 4b are made of Ta ₂ O ₅ , and the light loss means is made of a metal film of gold, silver, copper, nickel, lead, aluminum, chromium, or titanium. .
In addition, reactive ion etching or back sputtering is performed on the interfaces of the clads 4a and 4b in contact with the optical loss means 7a and 7b in order to enhance the loss effect.

  As described above, the optical waveguide Q-switching element 1 has a planar waveguide structure, which facilitates downsizing. That is, since the thickness (size in the y-axis direction) of the electro-optic crystal can be reduced by the optical waveguide 3 having a planar waveguide structure, low voltage driving is possible, and light propagation in the optical waveguide 3 is further improved. By using it, a high extinction ratio can be realized.

  Furthermore, at least one of the upper and lower clads 4a and 4b has a tapered shape such that the thickness in the vertical direction (y-axis direction) gradually increases from the light incident surface of the optical waveguide 3 toward the light emitting surface. The transparent block 8 (FIGS. 9 to 11) is configured.

  Thus, since the number of reflections in the optical waveguide 3 can be reduced by using the tapered transparent block 8 (FIGS. 9 to 11) instead of the optical loss means 7a, the optical waveguide type Q is further reduced. Miniaturization of the switch element 1 can be realized.

  According to the first embodiment of the present invention, the refractive index difference between the optical waveguide 3 and the clads 4a and 4b is reversed by using light deflection due to the electro-optic effect or the refractive index change in the optical waveguide 3 due to electric field application. Since the optical confinement function of the clads 4a and 4b is removed, an optical waveguide type Q-switch element realizing a high extinction ratio and miniaturization can be obtained without using a Pockels cell or a saturable absorber using polarized light.

Embodiment 2. FIG.
In the first embodiment (FIGS. 1 to 11), the electrodes 2a and 2b are provided on the outer upper and lower surfaces in the y-axis direction of the claddings 4a and 4b. However, as shown in FIGS. The electrodes 12a and 12b may be provided on the side surface in the x-axis direction of 14b.

12 is a perspective view showing an optical waveguide type Q switch element 11 according to Embodiment 2 of the present invention, and FIG. 13 is a cross-sectional view taken along line CC ′ in FIG.
14 and 15 are explanatory views showing the operation according to the second embodiment of the present invention in a cross-sectional view. FIG. 14 shows the operation of the optical waveguide Q switch element 11 when no electric field is applied. Reference numeral 15 denotes the operation of the optical waveguide type Q switch element 11 when an electric field is applied.

12-15, the same code | symbol shows the same or an equivalent part. The elements indicated by the reference numerals 11 to 16 correspond to the elements of the reference numerals 1 to 6 described above (FIG. 1).
12 and 13, the optical waveguide type Q switch element 11 has a planar waveguide structure, as described above, and includes an optical waveguide 13 composed of electrodes 12a and 12b, clads 14a and 14b, and a core 15. , Q switch driving device 16.

As described above, clads 14a and 14b are provided on both end faces (upper and lower faces) of the core 15 parallel to the xz plane.
The x axis is a slow axis with respect to the optical waveguide 13, the y axis is a fast axis with respect to the optical waveguide 13, and the z axis is parallel to the optical axis with respect to the optical waveguide 13.

  In this case, first and second electrodes 12a and 12b are provided on both side surfaces (yz plane) perpendicular to the xz plane of the core 15, and both the electrodes 12a and 12b are The Q switch driving device 16 is electrically connected.

Next, the operation according to the second embodiment of the present invention shown in FIGS. 12 and 13 will be described with reference to FIGS.
First, as shown in FIG. 14, when no electric field is applied between the electrodes 12a and 12b, when the light L1 is incident from the incident surface 15a of the core 15, the y-axis direction is the same as described above (FIG. 3). Since the refractive index of the core 15 is higher than the refractive indexes of the upper cladding 14a and the lower cladding 14b, the critical angle at the interface between the core 15 and the upper cladding 14a and the interface between the core 15 and the lower cladding 14b is larger than the critical angle. Total reflection is performed with respect to optical waveguide mode light having a low propagation angle.

Therefore, when no electric field is applied (FIG. 14), the incident light L1 in the y-axis direction propagates through the optical waveguide 13 with almost no loss, and is emitted from the exit surface 15b of the core 15 as the exit light L2.
Further, with respect to the x-axis direction, the light L1 propagates parallel to the z-axis direction, and is emitted from the emission surface 15b of the core 15 as light L2.

On the other hand, when an electric field is applied between the electrode 12a and the electrode 12b as shown in FIG. 15, when the light L1 is incident from the incident surface 15a of the core 15, the propagation operation in the y-axis direction is the same as that described above (FIG. 14). However, in the x-axis direction, the refractive index on the high potential side (electrode 12a side) of the core 15 is lowered due to the electro-optic effect, so that the incident light L1 is deflected to the low potential side.
Therefore, the outgoing light L2 is emitted in a state of being refracted toward the electrode 12b on the outgoing surface 15b of the core 15.

  As described above, the optical waveguide type Q switch element 11 according to the second embodiment (FIGS. 12 to 15) of the present invention includes the optical waveguide 13 having the planar waveguide structure including the core 15 and the clads 14a and 14b, and the optical waveguide. Electrodes 12a and 12b provided on both side surfaces of the waveguide 13 and a Q switch driving device 16 that applies a voltage to the electrodes 12a and 12b so as to be turned on and off are provided.

The core 15 is made of a material having an electro-optic crystal, and the clads 14a and 14b are provided on the upper and lower surfaces of the core 15 to confine the light L1 in the core 15, and have a lower refractive index than the material of the core 15. Made of material.
The electrodes 12a and 12b are made of a material having high electrical conductivity, and are provided on both side surfaces (yz plane) perpendicular to the xz plane of the core 15 and are electrically connected to the Q switch driving device 16. ing.

  Thus, by inserting the optical waveguide type Q switch element 11 into the resonator and deflecting the light L1 with respect to the optical axis direction so as to prevent resonance in the x-axis direction during excitation (FIG. 15), a high An efficient Q switch operation can be realized.

Embodiment 3 FIG.
In the second embodiment (FIGS. 12 to 15), the rectangular parallelepiped core 15 is used. However, as shown in FIGS. 16 to 19, the core 25 having a taper shape in the x-axis direction may be used. Good.

16 is a perspective view showing an optical waveguide type Q switch element 21 according to Embodiment 3 of the present invention, and FIG. 17 is a cross-sectional view taken along the line DD ′ in FIG.
FIGS. 18 and 19 are cross-sectional views illustrating the operation according to the third embodiment of the present invention. FIG. 18 illustrates the operation of the optical waveguide Q switch element 21 when no electric field is applied. Reference numeral 19 denotes the operation of the optical waveguide type Q switch element 21 when an electric field is applied.

16 to 19, the same reference numerals indicate the same or corresponding parts. The elements indicated by the reference numerals 21 to 26 correspond to the elements of the reference numerals 11 to 16 described above (FIG. 12).
16 and 17, an optical waveguide type Q switch element 21 has a planar waveguide structure, as described above, and includes an optical waveguide 23 composed of electrodes 22a and 22b, clads 24a and 24b, and a core 25. And a Q switch driving device 26 for applying a voltage to the electrodes 22a and 22b so as to be turned on and off.

Claddings 24 a and 24 b are provided on both end faces (upper and lower faces) parallel to the xz plane of the core 25. Electrodes 22a and 22b are provided on both side surfaces (yz plane) perpendicular to the xz plane of the core 25, and the Q switch drive device 26 is electrically connected to both electrodes 22a and 22b. It is connected.
The x axis is a slow axis with respect to the optical waveguide 23, the y axis is a fast axis with respect to the optical waveguide 23, and the z axis is parallel to the optical axis with respect to the optical waveguide 23.

  In this case, in the optical waveguide 23, the cross-sectional shape of the core 25 is such that the dimension in the z-axis direction (length in the optical path direction) gradually decreases from the first electrode 22a toward the second electrode 22b. Have a tapered shape.

Next, the operation of the third embodiment of the present invention shown in FIGS. 16 and 17 will be described with reference to FIGS.
First, as shown in FIG. 18, in the case where an electric field is not applied between the electrodes 22a and 22b, when the light L1 is incident from the incident surface 25a of the core 25, the propagation of the light L1 in the y-axis direction is as follows. Is higher than the refractive indexes of the clads 24a and 24b, so that an optical waveguide having a propagation angle lower than the critical angle at the interface between the core 25 and the upper clad 24a and at the interface between the core 25 and the lower clad 24b. Total reflection with respect to mode light.

  Therefore, when no electric field is applied (FIG. 18), the incident light L1 in the y-axis direction propagates through the optical waveguide 23 with almost no loss and is parallel to the z-axis from the exit surface 25b of the core 25. Is emitted.

  On the other hand, regarding the propagation of the incident light L1 in the x-axis direction when no electric field is applied (FIG. 18), when the light L1 enters the incident surface 25a of the core 25, the refraction angle θ1 with respect to the z-axis direction due to refraction. In this state, the light propagates through the core 25, reaches the exit surface 25b of the core 25, and is further refracted, whereby the outgoing light L2 is emitted with a refraction angle θ2 with respect to the z axis.

  On the other hand, as shown in FIG. 19, when an electric field is applied between the electrodes 22a and 22b, the light L1 incident from the incident surface 25a of the core 25 has the propagation operation of the light L1 in the y-axis direction described above. (FIG. 18), but regarding the propagation of the light L1 in the x-axis direction, the refractive index on the high potential side (electrode 22a side) of the core 5 decreases due to the electro-optic effect. The light L1 tilted by the refraction angle θ1 is deflected to the low potential side (electrode 22b side) in the core 25.

  Therefore, when an electric field is applied (FIG. 19), the light L1 propagated in the core 25 is deflected so as to be parallel to the z-axis (θ2 = 0 °) when reaching the emission surface 25b. The light exits from the exit surface 25b.

  As described above, according to the third embodiment (FIGS. 16 to 19) of the present invention, the core 25 (optical waveguide 23) is connected to the second electrode 22a, 22b on both side surfaces from the first electrode 22a to the second electrode. Since the taper shape is such that the length in the z-axis direction (optical path direction) gradually decreases toward the electrode 22b, the inclination of the emitted light L2 with respect to the z-axis direction when an electric field is applied (FIG. 19). It can be 0 °.

Embodiment 4 FIG.
In the third embodiment (FIGS. 16 to 19), in the optical waveguide Q switch element 21 in which the electrodes 22a and 22b are provided on both side surfaces (yz planes) of the optical waveguide 23, the taper is in the x-axis direction. Although the core 25 having a shape is used, in the optical waveguide type Q switch element 31 in which the electrodes 32a and 32b are provided on the upper and lower surfaces (xz plane) of the optical waveguide 33 as shown in FIGS. A core 35 having a tapered shape in the axial direction may be used.

20 is a perspective view showing an optical waveguide type Q switch element 31 according to Embodiment 4 of the present invention, and FIG. 21 is a cross-sectional view taken along line EE ′ in FIG.
FIGS. 22 and 23 are explanatory views showing the operation according to the fourth embodiment of the present invention in a sectional view. FIG. 22 shows the operation of the optical waveguide type Q switch element 31 when no electric field is applied. Reference numeral 23 denotes the operation of the optical waveguide type Q switch element 31 when an electric field is applied.

20 to 23, the same reference numerals indicate the same or corresponding parts. The elements indicated by the reference numerals 31 to 37 correspond to the elements of the reference numerals 1 to 7 described above (FIG. 1).
20 and 21, an optical waveguide type Q switch element 31 has a planar waveguide structure, as described above, and includes an optical waveguide 33 composed of electrodes 32a and 32b, clads 34a and 34b, and a core 35. And a Q switch driving device 36 that applies a voltage to the electrodes 32a and 32b so as to be turned on and off.

  Clads 34 a and 34 b are provided on both end faces (upper and lower faces) parallel to the xz plane of the core 35. Further, light loss means 37 a and 37 b are provided on both end faces (upper and lower faces) parallel to the xz plane of the clads 34 a and 34 b and facing the core 35. Furthermore, electrodes 32a and 32b are provided on both end faces (upper and lower faces) parallel to the xz plane of the light loss means 37a and 37b and facing the clads 34a and 34b.

A Q switch driving device 36 is electrically connected to both the electrodes 32a and 32b.
The x axis is parallel to the optical waveguide 33, the y axis is fast to the optical waveguide 33, and the z axis is parallel to the optical waveguide 33.

In this case, in the optical waveguide 33, the core 35 has a taper shape such that the dimension in the z-axis direction gradually decreases in the y-axis direction from the first electrode 32a toward the second electrode 32b. .
The clad 34a, 34b is made of a material whose refractive index of the clads 34a, 34b is always lower than the refractive index of the core 35 regardless of whether or not an electric field is applied to the electrodes 32a, 32b.

Next, the operation according to the fourth embodiment of the present invention shown in FIGS. 20 and 21 will be described with reference to FIGS.
First, as shown in FIG. 22, when no electric field is applied between the electrode 32a and the electrode 32b, regarding the propagation of the light L1 in the y-axis direction, if the light L1 is incident on the incident surface 35a of the core 35, it is refracted. As a result, the light is inclined by the refraction angle θ1 with respect to the z-axis direction and is incident on the upper clad 34a.

At this time, since the propagation angle becomes larger than the critical angle at the interface between the core 35 and the upper surface cladding 34a and the interface between the core 35 and the lower surface cladding 34b, the light L1 is transmitted through the claddings 34a and 34b. The light is incident on the light loss means 37a and 37b, and a part of the light is attenuated and reflected by the light loss means 37a and 37b.
Thereafter, the reflection is repeated many times, and finally the light L2 is emitted from the emission surface 35b after further refracting on the emission surface 35b of the core 35.

On the other hand, when an electric field is applied between the electrode 32a and the electrode 32b as shown in FIG. 23, when the light L1 is incident from the incident surface 35a of the core 35, the propagation operation of the light L1 in the y-axis direction is as described above ( As in FIG. 22), regarding the propagation of light L1 in the x-axis direction, the refractive index on the high potential side (electrode 32a side) decreases due to the electro-optic effect, so only the refraction angle θ1 with respect to the z-axis direction. The tilted light L1 is deflected in the core 35 to the low potential side (electrode 32b side).
Therefore, when the core 35 reaches the emission surface 35b, the emission light L2 is deflected so as to be parallel to the z-axis direction (θ2 = 0 °) and emitted from the emission surface 35b.

  As described above, according to the fourth embodiment of the present invention (FIGS. 20 to 23), the optical waveguide 33 having the planar waveguide structure including the core 35 and the clads 34a and 34b, and the upper and lower surfaces of the optical waveguide 33 are provided. Light loss means 37a, 37b and electrodes 32a, 32b, and a Q switch drive device 36 for applying a voltage to the electrodes 32a, 32b so as to be turned on and off.

The clads 34a and 34b are provided on the upper and lower surfaces of the core 35 in order to confine the light L1 in the core 35, and are made of a material whose refractive index is always lower than that of the core 35.
The light loss means 37a and 37b are made of a material or a structure that attenuates light when the light L1 comes into contact, and are provided on both end faces that are parallel to the plane of the clads 34a and 34b and face the core 35.

The electrodes 32a and 32b are made of a material having high electrical conductivity, are provided on both end faces that are parallel to the plane of the optical loss means 37a and 37b and face the clads 34a and 34b, and are electrically connected to the Q switch drive device 36. Connected.
The core 35 is made of a material having an electro-optic crystal, and the optical waveguide 33 is formed in the z-axis direction (optical path direction) from the first electrode 32a to the second electrode 32b of the electrodes 32a and 32b on both end faces. ) Has a tapered shape that gradually decreases.
Thereby, at the time of electric field application (FIG. 23), the inclination with respect to the z-axis direction of the emitted light L2 can be set to 0 °.

Embodiment 5 FIG.
In the first to fourth embodiments (FIGS. 1 to 23), the optical waveguide type Q switch element has been described. However, as shown in FIG. 24, the optical waveguide type Q switch element 1 described above (FIG. 1) is used. The Q-switch laser device 40 may be configured by using it.

FIG. 24 is a perspective view showing a Q-switch laser apparatus 40 according to Embodiment 5 of the present invention.
In FIG. 24, the Q switch laser device 40 includes an optical waveguide type Q switch element 1, an excitation light source 41 that emits excitation light Lp, and a plane that converts the excitation light Lp into incident light to the optical waveguide type Q switch element 1. Waveguide type laser medium 42, excitation light source 41, planar waveguide type laser medium 42, heat sink 43 on which optical waveguide type Q switch element 1 is mounted, and Q switch that applies an electric field to optical waveguide type Q switch element 1 A driving device 46, a first reflecting means (not shown), and a second reflecting means 45 that emits the oscillation light Lo are provided.

  The excitation light source 41, the planar waveguide type laser medium 42, the optical waveguide type Q switch element 1, and the second reflecting means 45 constitute a laser light source of the Q switch laser device 40.

The planar waveguide type laser medium 42 has the same optical waveguide thickness as the optical waveguide type Q switch element 1.
The excitation light source 41, the planar waveguide type laser medium 42, and the optical waveguide type Q switch element 1 are arranged close to each other.

In FIG. 24, although not shown in order to avoid complication, the first reflecting means is provided on the end surface of the planar waveguide laser medium 42 on the excitation light source 41 side, and reflects the excitation light Lp. And has a function of totally reflecting the oscillation light Lo.
The second reflecting means 45 has a function of partially reflecting the oscillation light Lo, and cooperates with the first reflecting means, the planar waveguide type laser medium 42 and the optical waveguide type Q switch element 1. Thus, a laser resonator is formed.

  On the heat sink 43, the elements are arranged in the order of the excitation light source 41, the second reflecting means, the planar waveguide type laser medium 42, and the optical waveguide type Q switch element 1, and further, the optical waveguide type Q switch element. The second reflecting means 45 is disposed on the first emission end face.

The excitation light source 41 has a plurality of emitters and an oscillation wavelength having a small divergence angle with respect to the planar direction of the planar waveguide laser medium 42 and having an oscillation wavelength that allows the planar waveguide laser medium 42 to be satisfactorily absorbed. It is desirable to use one that outputs 41.
Here, an LD (Laser Diode) array is used as the excitation light source 41.

  As the planar waveguide laser medium 42, it is desirable to use a planar waveguide medium that has a planar structure, has a high gain with respect to the wavelength of the excitation light Lp, and is excellent in mechanical strength and thermal conductivity.

Next, the operation of the Q-switch laser apparatus 40 according to the fifth embodiment of the present invention shown in FIG. 24 will be described with reference to FIGS.
The excitation light Lp emitted from the excitation light source 41 is incident on the planar waveguide type laser medium 42, and the excitation light Lp incident on the planar waveguide type laser medium 42 propagates through the optical waveguide 3 in the vertical direction, and in the planar direction. To spatially propagate and optically excite the inside of the planar waveguide type laser medium 42.

  At the start of excitation, the spontaneous emission light generated in the planar waveguide laser medium 42 is generated by driving the Q switch driving device 46 electrically connected to the electrodes 2a and 2b of the optical waveguide Q switch element 1. Then, it is deflected from the optical axis by the optical waveguide type Q switch element 1 (FIG. 4).

  In this way, a part of light is leaked from the gap between the planar waveguide type laser medium 42 and the optical waveguide type Q switch element 1 to lose the feedback function of the resonator, thereby suppressing laser oscillation. .

  After that, when the driving of the Q switch driving device 46 is stopped after the energy in the planar waveguide type laser medium 42 is sufficiently accumulated, the optical waveguide type Q switching element 1 is not deflected. The optical waveguide mode light having a propagation angle lower than the critical angle is totally reflected at the interface between the core 5 and the clads 4a and 4b.

Thereby, since the light L1 can propagate through the optical waveguide 3 with almost no loss, the Q value in the resonator is rapidly improved.
As described above, when the gain is higher than the loss, the number of photons rapidly increases in the resonator, and a pulse with a high peak value is generated. Therefore, it is provided on the output end face of the optical waveguide type Q switch element 1. In the second reflecting means 45, a part of the light generated in the resonator is extracted as oscillation light Lo and oscillates as an output pulse.

  In FIG. 24, the second reflecting means 45 is provided. However, in order to reduce the number of parts, an optical waveguide type Q switching element is used instead of the second reflecting means 45 (FIG. 24) as shown in FIG. A reflective coating (not shown) may be applied to one exit surface 5b.

  In FIG. 25, a reflective coating (not shown) that functions as the second reflecting means 45 is provided on the opposite side (outgoing surface 5b) of the optical waveguide Q-switch element 1 from the incident surface 5a with respect to the planar waveguide laser medium 42. Z).

  As described above, the Q-switch laser apparatus 40 according to Embodiment 5 (FIGS. 24 and 25) of the present invention includes the optical waveguide type Q-switch element 1 and has a planar structure laser light source (excitation) that generates laser light. Since the light source 41, the planar waveguide type laser medium 42, the optical waveguide type Q switch element 1 and the second reflecting means 45) are provided, the laser beam width can be expanded in the lateral direction and matching with the LD array. High power, easy power scaling, and high output.

  In FIGS. 24 and 25, the Q switch element 1 of the first embodiment (FIG. 1) is used as the laser light source of the Q switch laser device 40. However, the Q switches according to the other embodiments 2 to 4 are used. Switch elements 11, 21, 31 may be used.

Whichever Q switch element is used, it is easy to reduce the size and has a high extinction ratio, so that high-efficiency operation can be realized, and the thickness of the electro-optic crystal (core) is reduced by using an optical waveguide. Therefore, Q switch driving and electrical switching by applying a low voltage are possible, and accurate timing control of pulse laser output is possible.
Further, by using the planar waveguide laser medium 42 having a planar structure, high output can be achieved.

1, 11, 21, 31 Optical waveguide type Q switch, 2a, 2b, 12a, 12b, 22a, 22b, 32a, 32b Electrode, 2a, 12a, 22a, 32a First electrode, 2b, 12b, 22b, 32b First 2 electrodes 3, 13, 23, 33 Optical waveguide, 4a, 4b, 14a, 14b, 24a, 24b, 34a, 34b Cladding, 4a, 14a, 24a, 34a Upper surface cladding, 4b, 14b, 24b, 34b Lower surface cladding 5, 15, 25, 35 Core, 5a, 15a, 25a, 35a Core entrance surface, 5b, 15b, 25b, 35b Core exit surface, 6, 16, 26, 36, 46 Q-switch drive device, 7a, 7b, 37a, 37b Light loss means, 8 transparent block, 8b end face of transparent block, 40 switch laser device, 41 excitation light source, 42 planar waveguide Laser medium, 43 heat sink, 45 second reflection means, L1 incident light, L2 emitted light, Lo oscillation light, Lp excitation light, _{n 1} the refractive index, _{n 2} the refractive index, _{n o} refractive index, .theta.1 refraction angle, .theta.2 refraction Horn.

Claims (9)

An optical waveguide having a planar waveguide structure including a core and a clad, optical loss means and electrodes provided on the upper and lower surfaces of the optical waveguide, and a Q switch driving device that applies a voltage to the electrodes in an on / off manner. An optical waveguide type Q switch element,
The cladding is provided on the upper and lower surfaces of the core to confine light in the core,
The light loss means is made of a material or structure that attenuates light when contacted with light, and is provided on both end faces parallel to the plane of the clad and facing the core,
The electrode is made of a material having high electrical conductivity, is provided on both end faces that are parallel to the plane of the light loss means and that faces the clad, and is electrically connected to the Q switch driving device,
The core has an electro-optic crystal and is made of a material whose refractive index changes due to an electro-optic effect when an electric field is applied between the electrodes on both end faces.
The refractive index in the core is
When the electric field is not applied, it is higher than the refractive index of the upper and lower clads,
When a positive electric field is applied between the electrodes on both end faces, the upper electrode becomes a high potential and the lower electrode becomes a low potential, the refractive index is lower than the refractive index of the upper clad and the lower surface Higher than the cladding's refractive index,
When a negative electric field is applied between the electrodes on the both end faces, the upper electrode becomes a low potential, and the lower electrode becomes a high potential, the refractive index of the lower clad is lower, and An optical waveguide type Q switch element characterized by having a refractive index higher than that of the clad on the upper surface. The optical waveguide is made of KTN,
The optical waveguide type Q switch element according to claim 1, wherein the clad is made of Ta ₂ O ₅ .   3. The optical waveguide type Q switch element according to claim 1, wherein the light loss means is made of a metal film of gold, silver, copper, nickel, lead, aluminum, chromium, or titanium.   4. The optical waveguide type Q switch element according to claim 1, wherein reactive ion etching or back sputtering is performed on an interface of the clad in contact with the optical loss means. 5. .   At least one of the upper and lower claddings is formed of a tapered transparent block whose thickness in the vertical direction gradually increases from the light incident surface to the light emitting surface of the optical waveguide. The optical waveguide type Q switch element according to any one of claims 1 to 4. Optical waveguide type Q comprising: an optical waveguide having a planar waveguide structure composed of a core and a clad; electrodes provided on both side surfaces of the optical waveguide; and a Q switch driving device that applies a voltage to the electrodes in an on / off manner. A switch element,
The core is made of a material having an electro-optic crystal,
The clad is provided on the upper and lower surfaces of the core in order to confine light in the core, and is made of a material having a refractive index lower than that of the core.
The electrode is made of a material having high electrical conductivity, is provided on both side surfaces perpendicular to the plane of the core, and is electrically connected to the Q switch driving device. element.   The optical waveguide has a tapered shape such that the length in the optical path direction gradually decreases from the first electrode surface to the second electrode surface among the electrodes on both end surfaces. The optical waveguide type Q switch element according to claim 6. An optical waveguide having a planar waveguide structure including a core and a clad, optical loss means and electrodes provided on the upper and lower surfaces of the optical waveguide, and a Q switch driving device that applies a voltage to the electrodes in an on / off manner. An optical waveguide type Q switch element,
The clad is provided on the upper and lower surfaces of the core to confine light in the core, and is made of a material whose refractive index is always lower than that of the core.
The light loss means is made of a material or structure that attenuates light when contacted with light, and is provided on both end faces that are parallel to the plane of the cladding and that face the core,
The electrode is made of a material having high electrical conductivity, is provided on both end faces that are parallel to the plane of the light loss means and that faces the clad, and is electrically connected to the Q switch driving device,
The core is made of a material having an electro-optic crystal,
The optical waveguide has a tapered shape such that the length in the optical path direction gradually decreases from the first electrode surface to the second electrode surface among the electrodes on both end surfaces. Optical waveguide type Q switch element.   A Q-switched laser device comprising a planar structure laser light source including the optical waveguide type Q-switch element according to any one of claims 1 to 8 and generating laser light.

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